Fair Value of Financial Instruments - Fair Value of Financial Instruments (Detail) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Carrying Amount | MidCap Credit Facility
Financial liabilities:
Total financial liabilities fair value	$ 33.0	$ 39.3
Carrying Amount | Senior Convertible Notes
Financial liabilities:
Total financial liabilities fair value	226.9	225.4
Carrying Amount | Mann Group Convertible Notes
Financial liabilities:
Total financial liabilities fair value	8.8	8.8
Carrying Amount | Milestone Rights
Financial liabilities:
Total financial liabilities fair value	3.9	4.8
Carrying Amount | Contingent Milestone Liability
Financial liabilities:
Total financial liabilities fair value	0.3	0.6
Carrying Amount | Financing Liability
Financial liabilities:
Total financial liabilities fair value	104.1	104.1
Estimate of Fair Value Measurement | Fair Value, Inputs, Level 3 | MidCap Credit Facility
Financial liabilities:
Total financial liabilities fair value	35.5	41.1
Estimate of Fair Value Measurement | Senior Convertible Notes | Fair Value, Inputs, Level 3
Financial liabilities:
Total financial liabilities fair value	231.3	253.9
Estimate of Fair Value Measurement | Mann Group Convertible Notes | Fair Value, Inputs, Level 3
Financial liabilities:
Total financial liabilities fair value	14.4	20.8
Estimate of Fair Value Measurement | Milestone Rights | Fair Value, Inputs, Level 3
Financial liabilities:
Total financial liabilities fair value	11.9	12.6
Estimate of Fair Value Measurement | Contingent Milestone Liability | Fair Value, Inputs, Level 3
Financial liabilities:
Total financial liabilities fair value	0.3	1.0
Estimate of Fair Value Measurement | Financing Liability | Fair Value, Inputs, Level 3
Financial liabilities:
Total financial liabilities fair value	$ 106.8	$ 103.2